1. Technical Field
This invention relates generally to procedures and equipment for stopping an existing water, sewer, or gas line containing fluid under pressure, and more particularly to a method and associated componentry for inserting a valve in a line without otherwise shutting down the line during insertion.
2. Description of Related Art
To visualize some of the problems of existing methods for valve insertion, consider the known vertical insertion technique for installing a gate valve into an existing water pipe. First, workmen install a cutter tool over the pipe at the insertion point and a jacking clamp adjacent to it. Next, they install a water-tight housing over the cutter tool. The housing includes a lower chamber that surrounds the cutter tool and an upper chamber into which the cutter is withdrawn after the pipe is cut.
With those components in place, the workmen operate the cutter to cut a section from the existing pipe. After doing that, they operate a lifting rod on the housing to raise the cutter tool and the freshly cut section into the upper chamber of the housing. Then, they operate a slide gate that seals the upper chamber from the lower chamber. With the upper chamber sealed off that way, they open the upper chamber and remove the cutter tool and section of pipe.
After removing the section of pipe, the workmen proceed to install the gate valve in its place. To do so, they first place the gate valve in the upper chamber of the housing and connect it to the lifting rod. Next, they close the upper chamber, open the slide gate, and operate the lifting rod to lower the gate valve into the position previously occupied by the removed section of pipe. With the gate valve in position, the workmen then operate the jacking clamp to seal the newly installed gate valve in place.
The foregoing description makes many problems evident. The two-chamber housing and jacking clamp components can be large, complicated, and expensive, for example, and require skill, time, and space to install. In addition, the gate valve must be specially designed for installation with the jacking clamp apparatus. Other existing techniques and componentry have similar problems. Thus, users need a better technique and associated componentry for inserting a valve in an existing line.